A crystal oscillator causes an inverse piezoelectric phenomenon in which the oscillator oscillates when a voltage is applied thereto. It is known that when a substance adheres to a surface of the crystal oscillator, the weight of the crystal oscillator part is changed and the frequency of the crystal oscillator is lowered. A method of measuring the weight of an adhered substance from the change in the frequency is a weight sensor using QCM.
There is disclosed a concentration sensor for detecting a concentration of a substance to be detected in a mixed solution in which a predetermined substance to be detected is dissolved in a predetermined solvent which includes: a crystal oscillator of which natural frequency changes according to the change in the concentration of the substance to be detected; and an oscillating circuit causing the crystal oscillator to oscillate. In the concentration sensor, the crystal oscillator is impregnated with the mixed solution so as to cause the crystal oscillator to oscillate and the natural frequency of the crystal oscillator at this time is obtained. As a result, the concentration of the substance to be detected in the mixed solution is obtained (Patent Document 1).
There is disclosed a detecting sensor in which a cyclodextrin derivative, which is combined with a specific substance, is fixed to an electrode provided in the crystal oscillator. The cyclodextrin derivative is fixed by a disulfide compound or a thiol compound (Patent Document 2).
There is described that using a QCM sensor, sublimates in some types of lower layer antireflection film were determined quantity under the heating at 200° C. and compared. It is reported that in measuring the sublimate of an antireflection film applied to a 4 inches wafer, the difference between the materials could be confirmed by baking and measuring dozens of wafers (Non-Patent Document 1).
Patent Document 1: Japanese Patent Application Publication No. JP-A-6-18394 (claims)
Patent Document 2: Japanese Patent Application Publication No. JP-A-2004-177258 (claims)
Non-Patent Document 1: SPIE Vol. 5753, pp. 655-662 (2005)